The present invention relates to a method of preparing 3-methyl pyridine from 2-methyl-1,5-diaminopentane or from a mixture of 2-methyl-1,5-diaminopentane and 3-methyl piperidine.
3-Methyl pyridine can be obtained by the reaction of aliphatic aldehydes with ammonia. (Chem. Techn. 22 (1970) 679-80, 745-48; J. pr. Chem. 312 (1970) 849-52).
It is furthermore known that pyridine or substituted pyridines can be prepared by the dehydrogenation of piperidine or suitably substituted piperidines.
Thus, German Pat. No. 1,192,648 describes the preparation of pyridine from piperidine with the use of a palladium-containing catalyst. Platinum and nickel are also described as usable catalysts in the same publication.
According to T. Takata, Bull. Chem. Soc. Japan 35, (1962) No. 9, pages 138-43, 3-methyl pyridine can similarly be obtained by dehydrogenation from 3-methyl piperidine.
For the preparation of the starting compound 3-methyl piperidine, 2-methyl glutaric acid nitrile is reacted with sodium amide to produce methyl glutaroimidine, and this is treated with sodium, whereupon the formation of 3-methyl piperidine takes place via 3-methyl-2,6-diaminopiperidine as an intermediate product.
This complex laboratory method is theoretically interesting, but it is not practical for production in technical quantities.